The present invention relates to landing gear (alternatively known as jacking legs) for articulated trailers.
Landing gear for articulated trailers allows the raising, lowering and support of the forward end of the trailer in the engagement and disengagement from the prime mover (alternatively known as the tractor or truck) and allows the trailer to be freestanding whilst not in transit. In most instances the trailer itself is decoupled from a prime mover and then re-coupled to either the same prime mover or an another depending on the logistics appropriate to the use.
A typical scenario is where a trailer is delivered to a loading dock for loading. The trailer will typically be loaded up to twenty tons in weight, and in some instances up to twenty five tons, on one trailer. The prime mover positions the trailer in the loading dock. The operator will de-latch the kingpin from the turntable (alternatively known as the fifth wheel) and disconnect the service lines. The operator will then manually lower the legs of the landing gear. First the landing gear will be lowered to ground level in the higher speed selection of the typically two-speed geared landing gear arrangement. Once engaged with the ground the operator generally has no option other than to change to the lower speed selection where the operator will enjoy the significant increase in mechanical advantage afforded by the higher gear ratio. The operator will then with significant effort raise the forward end on the trailer to clear the trailer kingpin from the turntable of the prime mover. Once the trailer king pin is clear of the prime mover turntable the prime mover can be driven clear of the trailer to leave the trailer freestanding. The prime mover is then typically utilized elsewhere in a more productive role than being idle whilst the trailer is loaded.
The trailer will then be loaded which may take a portion of an hour or it may take several days. Once the trailer is loaded a prime mover will then return to the trailer for the removal from the loading dock. In many instances the prime mover will not be the same unit. In such cases the turntable height may not be identical or in other instances due to the poor stability of the ground on which the landing gear rests the trailer may have sunk. In either of these instances the height of the trailer will need to be adjusted to mate with the prime mover. The operator has the onerous task of manually winding the trailer either up or down to the necessary height. Once the trailer is at the correct height for engagement with the prime mover the operator can then locate the prime mover under the trailer, mating the kingpin with the turntable.
To prepare the trailer for transport the legs are manually raised in low speed until they are once again clear of the ground. Having cleared the ground the weight of the loaded trailer is transferred from the landing gear to the prime mover this then allows the landing gear to be changed by the operator to high speed for the legs to be raised to their full height. Raising to full height is necessary to allow ground clearance for traveling both on the road system and in some instances off the road system. Most known landing gear utilizes a two-speed operation and typically the increase in mechanical advantage enjoyed in low speed is in the order of ten to one over the high speed. Even with the advantages afforded by the two-speed operation the time to couple a trailer with a prime mover will find 15 minutes as not atypical. This is particularly so when a trailer is loaded to its limits which generally requires the operator to rest due to the physical fatigue associated with the manual effort required.
There are several teachings of prior art documenting many variations of powered drives that can be added to existing landing gear jacking legs at either the time of installation of the leg or a subsequent time. U.S. Pat. No. 5,451,076 to Burkhead, U.S. Pat. No. 5,299,829 to Rivers, Jr, et al, U.S. Pat. No. 5,050,845 Aline, et al and U.S. Pat. No. 5,004,267 to Busby teach of a pneumatic motor to provide the necessary motive force to rotate the crank shaft (drive shaft) of the landing gear prior art. U.S. Pat. No. 4,466,637 to Nelson teaches of a drive motor such as an electric motor whilst we learn from U.S. Pat. No. 4,097,840 to Chappelle of an electric drive motor. It is noted that all of this prior art has existed for some time yet there is no significant commercialization of this art. The pneumatic teachings have not been accepted due their complexity and expensive nature of their pneumatic componentry. The prior art teachings of electrical motors is cumbersome, weighty and dated in technology. All the prior art tends to be overly complex and does not readily mount up to all commercial landing gear currently available and used within the trucking industry. Most of the prior art requires a strong dependence on the provision of power from the prime mover, that is, the prime mover is required to be coupled to the trailer for the prior art to function.
It is these problems that have brought about the present invention.
According to the present invention there is provided a demountable drive mechanism for the landing gear of a semi-trailer, the landing gear including legs that are extendable and retractable by rotation of a drive shaft through a gear mechanism, the drive shaft being axially displaceable to change the ratio of the gear mechanism, the drive mechanism comprising an electric motor having an output shaft adapted to be coupled to the drive shaft of the landing gear assembly, the electric motor being coupled to the landing gear through a torque arm so that the electric motor can impart torque to the drive shaft, means to axially displace the drive shaft to change the gear ratio, and means to control operation of the electric motor and axial displacement of the drive shaft.
According to a further aspect of the invention there is provided a demountable drive mechanism for the landing gear of a semi-trailer, the landing gear including legs that are extendable and retractable by rotation of a drive shaft through a gear mechanism, the drive shaft being axially displaceable to change the ratio of the gear mechanism, the drive mechanism comprising an electric motor having an output shaft adapted to be coupled to the drive shaft of the landing gear assembly, the electric motor being coupled to the landing gear through a torque arm so that the electric motor can impart torque to the drive shaft, the mechanism being axially displaceable to axially displace the drive shaft to change the gear ratio, and means to control operation of the electric motor.